1. Field of the Invention:
This invention relates in general to centrifugal submersible pumps, and in particular to the means for conveying downward thrust on an impeller.
2. Description of the Prior Art
Submersible centrifugal pumps are used for pumping large volumes of fluid from oil wells. The pump assembly has a downhole electric motor that rotates a shaft extending through the pump. A plurality of pump stages extend through a tubular housing of the pump. Each pump stage has a stationary diffuser and an impeller that is mounted to the shaft for rotation.
In a mixed flow type, the impeller passages discharge upward and outward. The downward thrust on the impellers which occurs as a result of the fluid being discharged is conveyed to the diffuser through a thrust pad or thrust washer. The thrust washer is located on a shoulder of the diffuser that is outward of the intake of the impeller passages. A downward facing shoulder on each impeller contacts the thrust washer.
While this is successful, the downward thrust washer has a relatively large diameter because of its location. The large surface area of the downward thrust washer results in more friction being produced than if the diameter is smaller.